Actor Bryce Pinkham has fun posing for photos after a rehearsal of “Benny & Joon” in Balboa Park. (Eduardo Contreras/Union-Tribune)

There’s a lot more to the movie-turned-musical “Benny & Joon” than those character names can convey, from a focus on the broader meaning of family to a frank consideration of mental illness.

Actually, there are more key characters than those character names convey — including one who just about drives the whole story.

His name is Sam, and in the original 1993 “Benny & Joon” movie he was played by Johnny Depp.

Dropping into the lives of the whip-smart but psychologically fragile Juniper (aka “Joon”) and her devoted brother Benny, Sam manages to pry open the pair’s insular little world in ways both salutary and potentially disastrous.

In the Old Globe’s world-premiere musical adaptation of the offbeat romantic comedy, Sam is played by a Tony Award-nominated actor who in real life is at least as fervent a devotee of the comedic geniuses Charlie Chaplin and Buster Keaton as the quirky and mysterious Sam is on-screen.

“I hate to put too fine a point on it,” Bryce Pinkham is saying before a recent morning rehearsal for the show, which begins performances at the Balboa Park theater this week. “But it’s a dream for me.”

You might know Pinkham as the star of Broadway’s “A Gentleman’s Guide to Love and Murder,” the musical whose original production was co-produced by the Globe almost four years ago (although Pinkham didn’t join the show until its Broadway premiere).

He got to clown around some in that macabre comedy, which wound up winning the 2014 best-musical Tony and earned Pinkham a lead-actor nomination.

But “Benny & Joon” — adapted by Kirsten Guenther, with music by Nolan Gasser and lyrics by Mindi Dickstein — gives Pinkham a chance to pay homage to a comic tradition he not only reveres and has incorporated into his own art, but has even delved into academically.

The graduate of Boston College and the Yale School of Drama was still trying to decide between pursuing sports and theater when, early in his college career, a professor suggested he check out the distinctive, very physical performance style of the renowned theatrical clown Bill Irwin.

“I didn’t know who he was, so I watched his videos,” Pinkham recalls. “And I went, ‘Omigod — sports AND theater!’ And through studying Bill, I found a renewed interest in Buster and Charlie. (He adds with a self-deprecating laugh: “I call them by their first names as if I know them.”)

Pinkham wound up writing a thesis about physical comedy and the work of Chaplin, Keaton and Irwin.

“And I always wanted to find a way to do something with that professionally,” he says. “‘Gentleman’s Guide’ was the closest I’ve gotten to doing truly physical comedy – I was onstage the entire time, sweating my tail off. Never been in better shape.

“But when this came up, I said, all right, I have to look at this, because it’s too many things I want.

“To take a character who, like me, just found inspiration in (those icons), and filtered their view of the world through his own unique instrument, and let it come out in whatever ways he saw useful in the moment — that is exactly what I want to do.”

Siblings in spotlight

As Pinkham and Guenther, the show’s writer, chat in the Globe’s offices, both reflect on the way “Benny & Joon” — directed by Jack Cummings III, artistic chief of off-Broadway’s The Transport Group — puts the sibling relationship front and center.

Each of them can relate: Pinkham’s sister, who recently moved to San Diego, has been a strong presence in his life, and Guenther says she’s likewise very close with her brother.

Guenther also feels a deep connection to the fact that Joon (played at the Globe by Hannah Elless, opposite her fellow Broadway veteran Andrew Samonsky as Benny) struggles with a disability — and to the way that reality drives Joon and those around her to find strength they didn’t know they had.

Guenther has an uncle with cerebral palsy; his condition motivated his parents (Guenther’s grandparents) to build, more or less by hand, a center for the disabled in the L.A.-area community of La Puente.

It eventually became known as the San Gabriel Valley Training Center, and is now known as the Roland Center, in honor of Guenther’s late grandmother. Today it provides services for some 300 adults.

Having grown up witnessing (and participating in) her family’s devotion to her uncle and other people with disabilities, “this piece really spoke to me,” Guenther says.

While Joon’s condition goes unspecified in the movie, “something that was important to us was to name Joon’s illness,” says Guenther. So in the stage musical, it’s made clear she’s a functioning schizophrenic.

In other ways, Guenther says, the creators are sticking to the spirit of the movie — retaining such signature scenes as the moment where Sam and Joon cook grilled cheese sandwiches with a clothes iron.

Writer Kirsten Guenther (right) and actor Bryce Pinkham talk during a rehearsal of “Benny & Joon” at the Old Globe. (Eduardo Contreras/Union-Tribune)

As for the riddles surrounding Sam: “I was fascinated by the role in the film, but I also wanted to know more about this person. So we’ve tried to give him a back story,” while still preserving a sense of mystery.

Guenther was a relative latecomer to the creative team; a Bay Area resident, she had been a student of lyricist Dickstein (whose credits include “Little Women the Musical”) while earning a master’s at New York University, and traveled in some of the same circles as Gasser, a renowned musicologist and composer. (Globe artistic director Barry Edelstein calls the latter’s score for the show “incredibly sumptuous.”)

Her route to musical theater might be worthy of a show all its own: Guenther originally studied acting at the University of Southern California, and was somehow roped into writing a song for a new musical she’d been asked to appear in.

Skeptical of what would result, she nevertheless wound up writing an entire show with two friends, and was hooked.

Some time later, she acquired a plane ticket to Paris from her mom, who handled travel for the Hustler gentleman’s clubs and had an unused “stripper ticket.” Guenther loved it there so much she didn’t want to go back, so applied for a nanny job that somehow turned into a potential writing gig.

Problem: Guenther didn’t know French. So she ended up submitting an honest account of how badly she had botched her first assignment.

“They ended up hiring me because I was so bizarre,” Guenther recalls. “They said, ‘If you can guarantee to screw up once a week, we would like to offer you this column-slash-blog.”

And that’s how she landed a gig as a Paris-based freelancer for USA Today.

Listening in, Pinkham gets a huge kick out of that story, which he’s hearing for the first time. (He affects an over-the-top accent as he imagines her French admirers exclaiming, “We love it! She has never written before — perfect!”)

But he also finds wisdom in the go-for-broke sensibility it conveys — one that Pinkham argues is the ideal mindset for those daring to create a brand-new musical.

“It ties perfectly into what we do for a living,” he says. “You have to go into a rehearsal room willing to admit you don’t know.”

“Which I do every day!,” Guenther shoots back.

But Pinkham insists: “You have to. And there are so many people who can’t do that, who are so precious what they have.”

In the room where they’re dreaming up “Benny & Joon,” by contrast, there’s only one rule, says Pinkham: “The best idea wins.”

Movies to musicals at the Old Globe

Over the past couple of decades, the Globe has been a prime incubator of musicals adapted from (or at least inspired by) non-musical films — with “Benny & Joon” now being the latest. Here’s a look at the track record. (The first three listed, by the way, all went on to Broadway; the latter three have yet to get there.)